Automatic door locks intermittent

1st post. '93 Metro 1.0 EFI 2 Door hatchback. This vehicle has door locks that lock automatically at about 10MPH. They recently have become intermittent. Sometimes they will work correctly for days and sometimes not at all for days. Both doors either work or they don't...what I mean is the problem is not isolated to one door. I'm hoping someone can give me an idea where to look. I'm disabled now and I don't know much about cars but I repaired TV's and Communication equipment for 30 years so I know a little about electricity if someone can give me a push in the right direction.
I've got some books out of the local library but none of them seems to show the circuitry involved. Thanks

Hi Rich, I think we own the same car. Mine has the same problem. I have the Haynes manual but can't find anything in it about automatic door locks. I'm thinking that there may be a vacuum operated switch to activate a relay which mechanically locks the doors. Sometimes mine locks almost immediately when I start forward, other times I've driven a couple of city blocks and sometimes not at all. It wouldn't bother me that they don't always lock but I see it as an indication that something is wrong somewhere in the electrical or vacuum system.
I'm also trying to figure out how to get the radio far enough out of the dash so I can unplug the antenna. I need to replace the antenna and the Haynes book led me down the garden path. I guess a trip to the library is in order.
Maybe a real smart Metro owner,(is that an oxymoron?) will chime in and solve our problem.
Jude in Appalchian Ohio

Hi guys,

Hey Rich, I posted teh schematics for the power locks at http://www.geocities.com/bkotae/geolocks.htm so you can take a look.

As you will see on page 2 it appears that if 1 door is locked the system will see both doors as locked so its possible that system will not attempt to auto-lock. (is it possible the times the locks are not working that the passenger door was manually locked?).